1. Field of the Invention
The present invention relates to an adhesive useful in adhering metal, plastics, wood, cloth, paper, and the like. More particularly, the present invention relates to an adhesive having strong adhesiveness to various metals. Additionally, the present invention relates to the utilization of, in particular, waste polyester.
2. Description of the Prior Art
Since plastic wastes are generally weather-resistant, and are difficulty decomposed even though allowed to stand exposed to the natural elements, the diposal of the waste now becomes a social problem all over the world.
For example, with regard to polyolefin wastes, polybutadiene wastes, polystyrene wastes, or the like, attempts to obtain monomers by decomposition of the waste by heating have been conducted in Japan. Also, for disposal of polyethylene terephthalate wastes, several attempts have been made for the utilization thereof. For example, the following attempts have been investigated:
1. Recovery of monomers, i.e., terephthalic acid and ethylene glycol, by decomposition
2. Production of molding compositions by blending with other polymers
3. Production of moldings by the addition of a nucleus forming agent (For example, as disclosed in Japanese Patent Laid Open No. 751/1973, British Pat. No. 1,117,139, and the like.)
However, polyethylene terephthalate waste is mainly composed of those polyethylene terephthalates which have been subjected to biaxial stretching and rendered heat stable, and thus the waste is quite stable to chemical reagents, there are no suitable solvents for the waste, and the waste has a high heat-stability, particularly heat-resistance. Due to the above-described original physical properties of polyethylene terephthalate, polyethylene terephthalate wastes are rarely utilized for economic reasons and other reasons with the exception for the recovery of the basic monomers by the Method (1) above is partly attempted by polyethylene terephthalate producers, and, as a matter of fact, polyethylene terephthalate wastes are generally disposed of by burial.
Japanese Patent Publication No. 20313/1968 describes a process for the production of a copolyester suitable for an adhesive which comprises modifying polyethylene terephthalate with glycols to reduce the crystallinity thereof, for the purpose of utilizing polyethylene terephthalate waste. However, it has been found that the polyester produced by the above method has a small degree of crystallinity and when subjected to outdoor exposure, crystallization occurs, reducing the adhesive strength, that is, the polyester has poor weather-resistance.